1. Field of the Invention
The invention relates to a fuel cell separator with good adhesion between a film and a substrate, which has excellent corrosion resistance against the corrosive atmosphere in a battery environment, and more particularly, excellent corrosion resistance of an open portion for forming a manifold. The invention also relates to a manufacturing method of the fuel cell separator, and a fuel cell and a vehicle which use the separator.
2. Description of the Related Art
Fuel cells are used in vehicles such as automobiles, as well as in other fields. These fuel cells have various kinds of fuel cell separators. Because the atmosphere in a battery environment is a corrosive one, attempts have been made to develop technology to improve the anticorrosive properties and the like of fuel cell separators.
For example, in attempt to provide a polymer electrolyte membrane fuel cell that can solve conventional problems like reduced performance of a fuel cell due to corrosion from contact with liquid within liquid gas, Japanese Patent Application Publication No. JP-A-2002-25574 proposes a polymer electrolyte membrane fuel cell made from sheet metal, in which is formed a manifold to allow fuel gas to flow into and out of a central fuel gas flow path, and in which a fluorocarbon resin coating layer is formed on an end surface of the manifold. This fuel cell separator is first sprayed with a fluorocarbon resin so that it coats an end surface of an opening for forming a manifold provided on a metal separator substrate, and then undergoes a punching process.
With a fuel cell made with this kind of fuel cell separator, however, despite the fact that the manifold has a coating layer on it, corrosion starts to occur at a peripheral edge portion that is not completely coated as fuel gas flows in and out. Also, this fuel cell separator requires many manufacturing processes due to the need for the spraying and punching processes. In addition, the punching process of the end surface of the opening of the manifold must be precisely controlled.
Furthermore, technologies for giving a fuel cell separator anticorrosive properties have also been proposed which coat a precious metal material onto a metal separator substrate using a PVD or CVD method, or which coat resin material or the like, including conductive material, onto an electrode side by spraying or the like.
These technologies, however, have the following problems. That is, (1) corrosion occurs starting at the peripheral edge portion (edge portion) of the manifold formed from the open portion of the fuel cell separator. This is because with current surface treatment technology it is difficult to coat portions such as the peripheral edge portion of the manifold perfectly. (2) Applying a precious metal coating may result in reduced adhesion of a seal portion when an adhesive, for example, is used for sealing, which may lead to a leak or the like, ultimately resulting in a loss of fuel cell function. This is because when gold, for example, is used as a precious metal coating material, there are generally almost no adhesives that adhere well to gold. (3) When all but the seal portion is coated with a precious metal coating in order to solve the problem described in (2) above, that seal portion remains susceptible to corrosion. This is because without the precious metal coating, the seal portion cannot withstand the battery environment.